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We describe incident human immunodeficiency virus (HIV) and syphilis trends in men who have sex with men (MSM) and transgender women (TGW) presenting for HIV voluntary counseling and testing (VCT) services and sexually transmitted infection (STI) management at the Silom Community Clinic, Bangkok, Thailand. Clients underwent rapid HIV testing and syphilis rapid plasma reagin (RPR) testing. For incidence analysis, we included clients with >1 follow-up visit. Initial negative HIV with subsequent positive HIV defined incident HIV infection; incident syphilis infection was defined as negative RPR followed by positive RPR (titer ≥1:8) and confirmatory anti- Treponema pallidum antibodies. Calculation of incidence using Poisson regression assumed a uniform probability distribution throughout the seroconversion interval. From 15 September 2005 to 31 December 2015, we tested 10,158 clients for HIV and 10,324 for syphilis. Overall, 7109 clients tested HIV-seronegative and contributed 7157 person-years (PY). Three-hundred forty-seven incident HIV infections resulted in an incidence rate of 4.8 per 100 PY (95% confidence interval [CI] 4.4-5.4). We found an inverted U-shape trend of HIV incidence over time with a peak of 6.4 per 100 PY in quarter 2/2011 ( p < 0.01) (Poisson with RCS function, p = 0.001). Overall, 8713 clients tested seronegative for syphilis and contributed 8623 PY. The incidence of syphilis infection was 4.4 per 100 PY (95% CI 3.9-4.8). Despite an apparent decline in HIV incidence among MSM and TGW attending VCT services, syphilis incidence rose and remained high. Evaluating temporal trends of HIV and syphilis incidence provides an opportunity to evaluate epidemic trajectories and target limited program funding. We recommend focused HIV and STI prevention interventions for MSM in Bangkok.

Background: High HIV incidence has been detected among men who have sex with men (MSM) in Thailand, but the relationship and timing of HIV, herpes simplex virus 2 (HSV-2), and syphilis is unknown. This analysis measures incidence, temporal relationships, and risk factors for HIV, HSV-2, and syphilis among at-risk MSM in the Bangkok MSM Cohort Study., Methods: Between April 2006 and December 2010, 960 men negative for HIV, HSV-2, and syphilis at entry enrolled and contributed 12-60 months of follow-up data. Behavioral questionnaires were administered at each visit; testing for HIV antibody was performed at each visit, while testing for syphilis and HSV-2 were performed at 12 month intervals. We calculated HIV, HSV-2, and syphilis incidence, assessed risk factors with complementary log-log regression, and among co-infected men, measured temporal relationships between infections with Kaplan-Meier survival analysis and paired t-test., Results: The total number of infections and incidence density for HIV, HSV-2, and syphilis were 159 infections and 4.7 cases/100 PY (95 % Confidence Interval (CI): 4.0-5.4), 128 infections and 4.5/100 PY (95 % CI: 3.9-5.5), and 65 infections and 1.9/100 PY (95 % CI: 1.5-2.5), respectively. Among men acquiring >1 infection during the cohort period, mean time to HIV and HSV-2 infection was similar (2.5 vs. 2.9 years; p = 0.24), while syphilis occurred significantly later following HIV (4.0 vs. 2.8 years, p < 0.01) or HSV-2 (3.8 vs. 2.8 years, p = 0.04) infection. The strongest independent predictor of any single infection in adjusted analysis was acquisition of another infection; risk of syphilis (Adjusted Hazards Ratio (AHR) = 3.49, 95 % CI: 1.89-6.42) or HIV (AHR = 2.26, 95 % CI: 1.47-3.48) acquisition during the cohort was significantly higher among men with incident HSV-2 infection. No single independent behavioral factor was common to HIV, HSV-2, and syphilis acquisition., Conclusion: HIV and HSV-2 incidence was high among this Thai MSM cohort. However, acquisition of HIV and co-infection with either HSV-2 or syphilis was low during the time frame men were in the cohort. Evaluation of behavioral risk factors for these infections suggests different risks and possible different networks.

We report prevalence of Treponema pallidum (TP) seropositivity and herpes simplex virus type 2 (HSV-2) infection and risk factors associated with their prevalence in a cohort of men who have sex with men (MSM) in Bangkok, Thailand. Between April 2006 and March 2010 we enrolled Thai MSM into a cohort study based at the Silom Community Clinic, with baseline behavioural data and laboratory testing for sexually transmitted infections (STIs). Logistic regression was used to analyse risk factors associated with the prevalence of TP seropositivity and HSV-2 infection. From a total of 1544 enrolled men (mean age 26 years) TP, HSV-2 and HIV seropositive rates were 4.4%, 20.7% and 21.6%, respectively. After multivariable analysis, participating in group sex, reporting paying for sex, reporting sex with a casual partner in a park and being HSV-2 seropositive were associated with TP prevalence. Age ≥30 years, having less than a high school education, past use of recreational drugs, meeting casual sexual partners at a public venue (sauna) and TP seropositivity were associated with HSV-2 infection. The significant baseline prevalence of TP seropositivity and HSV-2 infection in this cohort demonstrates the need for screening and treatment of these STIs and targeted prevention interventions in Thai MSM in Bangkok.